net/sched/sch_fq_codel.c

   1 /*
   2  * Fair Queue CoDel discipline
   3  *
   4  *      This program is free software; you can redistribute it and/or
   5  *      modify it under the terms of the GNU General Public License
   6  *      as published by the Free Software Foundation; either version
   7  *      2 of the License, or (at your option) any later version.
   8  *
   9  *  Copyright (C) 2012 Eric Dumazet <edumazet@google.com>
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/types.h>
  14 #include <linux/kernel.h>
  15 #include <linux/jiffies.h>
  16 #include <linux/string.h>
  17 #include <linux/in.h>
  18 #include <linux/errno.h>
  19 #include <linux/init.h>
  20 #include <linux/skbuff.h>
  21 #include <linux/jhash.h>
  22 #include <linux/slab.h>
  23 #include <linux/vmalloc.h>
  24 #include <net/netlink.h>
  25 #include <net/pkt_sched.h>
  26 #include <net/flow_keys.h>
  27 #include <net/codel.h>
  28
  29 /*      Fair Queue CoDel.
  30  *
  31  * Principles :
  32  * Packets are classified (internal classifier or external) on flows.
  33  * This is a Stochastic model (as we use a hash, several flows
  34  *                             might be hashed on same slot)
  35  * Each flow has a CoDel managed queue.
  36  * Flows are linked onto two (Round Robin) lists,
  37  * so that new flows have priority on old ones.
  38  *
  39  * For a given flow, packets are not reordered (CoDel uses a FIFO)
  40  * head drops only.
  41  * ECN capability is on by default.
  42  * Low memory footprint (64 bytes per flow)
  43  */
  44
  45 struct fq_codel_flow {
  46         struct sk_buff    *head;
  47         struct sk_buff    *tail;
  48         struct list_head  flowchain;
  49         int               deficit;
  50         u32               dropped; /* number of drops (or ECN marks) on this flow */
  51         struct codel_vars cvars;
  52 }; /* please try to keep this structure <= 64 bytes */
  53
  54 struct fq_codel_sched_data {
  55         struct tcf_proto *filter_list;  /* optional external classifier */
  56         struct fq_codel_flow *flows;    /* Flows table [flows_cnt] */
  57         u32             *backlogs;      /* backlog table [flows_cnt] */
  58         u32             flows_cnt;      /* number of flows */
  59         u32             perturbation;   /* hash perturbation */
  60         u32             quantum;        /* psched_mtu(qdisc_dev(sch)); */
  61         struct codel_params cparams;
  62         struct codel_stats cstats;
  63         u32             drop_overlimit;
  64         u32             new_flow_count;
  65
  66         struct list_head new_flows;     /* list of new flows */
  67         struct list_head old_flows;     /* list of old flows */
  68 };
  69
  70 static unsigned int fq_codel_hash(const struct fq_codel_sched_data *q,
  71                                   const struct sk_buff *skb)
  72 {
  73         struct flow_keys keys;
  74         unsigned int hash;
  75
  76         skb_flow_dissect(skb, &keys);
  77         hash = jhash_3words((__force u32)keys.dst,
  78                             (__force u32)keys.src ^ keys.ip_proto,
  79                             (__force u32)keys.ports, q->perturbation);
  80         return ((u64)hash * q->flows_cnt) >> 32;
  81 }
  82
  83 static unsigned int fq_codel_classify(struct sk_buff *skb, struct Qdisc *sch,
  84                                       int *qerr)
  85 {
  86         struct fq_codel_sched_data *q = qdisc_priv(sch);
  87         struct tcf_result res;
  88         int result;
  89
  90         if (TC_H_MAJ(skb->priority) == sch->handle &&
  91             TC_H_MIN(skb->priority) > 0 &&
  92             TC_H_MIN(skb->priority) <= q->flows_cnt)
  93                 return TC_H_MIN(skb->priority);
  94
  95         if (!q->filter_list)
  96                 return fq_codel_hash(q, skb) + 1;
  97
  98         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
  99         result = tc_classify(skb, q->filter_list, &res);
 100         if (result >= 0) {
 101 #ifdef CONFIG_NET_CLS_ACT
 102                 switch (result) {
 103                 case TC_ACT_STOLEN:
 104                 case TC_ACT_QUEUED:
 105                         *qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 106                 case TC_ACT_SHOT:
 107                         return 0;
 108                 }
 109 #endif
 110                 if (TC_H_MIN(res.classid) <= q->flows_cnt)
 111                         return TC_H_MIN(res.classid);
 112         }
 113         return 0;
 114 }
 115
 116 /* helper functions : might be changed when/if skb use a standard list_head */
 117
 118 /* remove one skb from head of slot queue */
 119 static inline struct sk_buff *dequeue_head(struct fq_codel_flow *flow)
 120 {
 121         struct sk_buff *skb = flow->head;
 122
 123         flow->head = skb->next;
 124         skb->next = NULL;
 125         return skb;
 126 }
 127
 128 /* add skb to flow queue (tail add) */
 129 static inline void flow_queue_add(struct fq_codel_flow *flow,
 130                                   struct sk_buff *skb)
 131 {
 132         if (flow->head == NULL)
 133                 flow->head = skb;
 134         else
 135                 flow->tail->next = skb;
 136         flow->tail = skb;
 137         skb->next = NULL;
 138 }
 139
 140 static unsigned int fq_codel_drop(struct Qdisc *sch)
 141 {
 142         struct fq_codel_sched_data *q = qdisc_priv(sch);
 143         struct sk_buff *skb;
 144         unsigned int maxbacklog = 0, idx = 0, i, len;
 145         struct fq_codel_flow *flow;
 146
 147         /* Queue is full! Find the fat flow and drop packet from it.
 148          * This might sound expensive, but with 1024 flows, we scan
 149          * 4KB of memory, and we dont need to handle a complex tree
 150          * in fast path (packet queue/enqueue) with many cache misses.
 151          */
 152         for (i = 0; i < q->flows_cnt; i++) {
 153                 if (q->backlogs[i] > maxbacklog) {
 154                         maxbacklog = q->backlogs[i];
 155                         idx = i;
 156                 }
 157         }
 158         flow = &q->flows[idx];
 159         skb = dequeue_head(flow);
 160         len = qdisc_pkt_len(skb);
 161         q->backlogs[idx] -= len;
 162         kfree_skb(skb);
 163         sch->q.qlen--;
 164         sch->qstats.drops++;
 165         sch->qstats.backlog -= len;
 166         flow->dropped++;
 167         return idx;
 168 }
 169
 170 static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 171 {
 172         struct fq_codel_sched_data *q = qdisc_priv(sch);
 173         unsigned int idx;
 174         struct fq_codel_flow *flow;
 175         int uninitialized_var(ret);
 176
 177         idx = fq_codel_classify(skb, sch, &ret);
 178         if (idx == 0) {
 179                 if (ret & __NET_XMIT_BYPASS)
 180                         sch->qstats.drops++;
 181                 kfree_skb(skb);
 182                 return ret;
 183         }
 184         idx--;
 185
 186         codel_set_enqueue_time(skb);
 187         flow = &q->flows[idx];
 188         flow_queue_add(flow, skb);
 189         q->backlogs[idx] += qdisc_pkt_len(skb);
 190         sch->qstats.backlog += qdisc_pkt_len(skb);
 191
 192         if (list_empty(&flow->flowchain)) {
 193                 list_add_tail(&flow->flowchain, &q->new_flows);
 194                 q->new_flow_count++;
 195                 flow->deficit = q->quantum;
 196                 flow->dropped = 0;
 197         }
 198         if (++sch->q.qlen < sch->limit)
 199                 return NET_XMIT_SUCCESS;
 200
 201         q->drop_overlimit++;
 202         /* Return Congestion Notification only if we dropped a packet
 203          * from this flow.
 204          */
 205         if (fq_codel_drop(sch) == idx)
 206                 return NET_XMIT_CN;
 207
 208         /* As we dropped a packet, better let upper stack know this */
 209         qdisc_tree_decrease_qlen(sch, 1);
 210         return NET_XMIT_SUCCESS;
 211 }
 212
 213 /* This is the specific function called from codel_dequeue()
 214  * to dequeue a packet from queue. Note: backlog is handled in
 215  * codel, we dont need to reduce it here.
 216  */
 217 static struct sk_buff *dequeue(struct codel_vars *vars, struct Qdisc *sch)
 218 {
 219         struct fq_codel_sched_data *q = qdisc_priv(sch);
 220         struct fq_codel_flow *flow;
 221         struct sk_buff *skb = NULL;
 222
 223         flow = container_of(vars, struct fq_codel_flow, cvars);
 224         if (flow->head) {
 225                 skb = dequeue_head(flow);
 226                 q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
 227                 sch->q.qlen--;
 228         }
 229         return skb;
 230 }
 231
 232 static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch)
 233 {
 234         struct fq_codel_sched_data *q = qdisc_priv(sch);
 235         struct sk_buff *skb;
 236         struct fq_codel_flow *flow;
 237         struct list_head *head;
 238         u32 prev_drop_count, prev_ecn_mark;
 239
 240 begin:
 241         head = &q->new_flows;
 242         if (list_empty(head)) {
 243                 head = &q->old_flows;
 244                 if (list_empty(head))
 245                         return NULL;
 246         }
 247         flow = list_first_entry(head, struct fq_codel_flow, flowchain);
 248
 249         if (flow->deficit <= 0) {
 250                 flow->deficit += q->quantum;
 251                 list_move_tail(&flow->flowchain, &q->old_flows);
 252                 goto begin;
 253         }
 254
 255         prev_drop_count = q->cstats.drop_count;
 256         prev_ecn_mark = q->cstats.ecn_mark;
 257
 258         skb = codel_dequeue(sch, &q->cparams, &flow->cvars, &q->cstats,
 259                             dequeue);
 260
 261         flow->dropped += q->cstats.drop_count - prev_drop_count;
 262         flow->dropped += q->cstats.ecn_mark - prev_ecn_mark;
 263
 264         if (!skb) {
 265                 /* force a pass through old_flows to prevent starvation */
 266                 if ((head == &q->new_flows) && !list_empty(&q->old_flows))
 267                         list_move_tail(&flow->flowchain, &q->old_flows);
 268                 else
 269                         list_del_init(&flow->flowchain);
 270                 goto begin;
 271         }
 272         qdisc_bstats_update(sch, skb);
 273         flow->deficit -= qdisc_pkt_len(skb);
 274         /* We cant call qdisc_tree_decrease_qlen() if our qlen is 0,
 275          * or HTB crashes. Defer it for next round.
 276          */
 277         if (q->cstats.drop_count && sch->q.qlen) {
 278                 qdisc_tree_decrease_qlen(sch, q->cstats.drop_count);
 279                 q->cstats.drop_count = 0;
 280         }
 281         return skb;
 282 }
 283
 284 static void fq_codel_reset(struct Qdisc *sch)
 285 {
 286         struct sk_buff *skb;
 287
 288         while ((skb = fq_codel_dequeue(sch)) != NULL)
 289                 kfree_skb(skb);
 290 }
 291
 292 static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = {
 293         [TCA_FQ_CODEL_TARGET]   = { .type = NLA_U32 },
 294         [TCA_FQ_CODEL_LIMIT]    = { .type = NLA_U32 },
 295         [TCA_FQ_CODEL_INTERVAL] = { .type = NLA_U32 },
 296         [TCA_FQ_CODEL_ECN]      = { .type = NLA_U32 },
 297         [TCA_FQ_CODEL_FLOWS]    = { .type = NLA_U32 },
 298         [TCA_FQ_CODEL_QUANTUM]  = { .type = NLA_U32 },
 299 };
 300
 301 static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt)
 302 {
 303         struct fq_codel_sched_data *q = qdisc_priv(sch);
 304         struct nlattr *tb[TCA_FQ_CODEL_MAX + 1];
 305         int err;
 306
 307         if (!opt)
 308                 return -EINVAL;
 309
 310         err = nla_parse_nested(tb, TCA_FQ_CODEL_MAX, opt, fq_codel_policy);
 311         if (err < 0)
 312                 return err;
 313         if (tb[TCA_FQ_CODEL_FLOWS]) {
 314                 if (q->flows)
 315                         return -EINVAL;
 316                 q->flows_cnt = nla_get_u32(tb[TCA_FQ_CODEL_FLOWS]);
 317                 if (!q->flows_cnt ||
 318                     q->flows_cnt > 65536)
 319                         return -EINVAL;
 320         }
 321         sch_tree_lock(sch);
 322
 323         if (tb[TCA_FQ_CODEL_TARGET]) {
 324                 u64 target = nla_get_u32(tb[TCA_FQ_CODEL_TARGET]);
 325
 326                 q->cparams.target = (target * NSEC_PER_USEC) >> CODEL_SHIFT;
 327         }
 328
 329         if (tb[TCA_FQ_CODEL_INTERVAL]) {
 330                 u64 interval = nla_get_u32(tb[TCA_FQ_CODEL_INTERVAL]);
 331
 332                 q->cparams.interval = (interval * NSEC_PER_USEC) >> CODEL_SHIFT;
 333         }
 334
 335         if (tb[TCA_FQ_CODEL_LIMIT])
 336                 sch->limit = nla_get_u32(tb[TCA_FQ_CODEL_LIMIT]);
 337
 338         if (tb[TCA_FQ_CODEL_ECN])
 339                 q->cparams.ecn = !!nla_get_u32(tb[TCA_FQ_CODEL_ECN]);
 340
 341         if (tb[TCA_FQ_CODEL_QUANTUM])
 342                 q->quantum = max(256U, nla_get_u32(tb[TCA_FQ_CODEL_QUANTUM]));
 343
 344         while (sch->q.qlen > sch->limit) {
 345                 struct sk_buff *skb = fq_codel_dequeue(sch);
 346
 347                 kfree_skb(skb);
 348                 q->cstats.drop_count++;
 349         }
 350         qdisc_tree_decrease_qlen(sch, q->cstats.drop_count);
 351         q->cstats.drop_count = 0;
 352
 353         sch_tree_unlock(sch);
 354         return 0;
 355 }
 356
 357 static void *fq_codel_zalloc(size_t sz)
 358 {
 359         void *ptr = kzalloc(sz, GFP_KERNEL | __GFP_NOWARN);
 360
 361         if (!ptr)
 362                 ptr = vzalloc(sz);
 363         return ptr;
 364 }
 365
 366 static void fq_codel_free(void *addr)
 367 {
 368         if (addr) {
 369                 if (is_vmalloc_addr(addr))
 370                         vfree(addr);
 371                 else
 372                         kfree(addr);
 373         }
 374 }
 375
 376 static void fq_codel_destroy(struct Qdisc *sch)
 377 {
 378         struct fq_codel_sched_data *q = qdisc_priv(sch);
 379
 380         tcf_destroy_chain(&q->filter_list);
 381         fq_codel_free(q->backlogs);
 382         fq_codel_free(q->flows);
 383 }
 384
 385 static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt)
 386 {
 387         struct fq_codel_sched_data *q = qdisc_priv(sch);
 388         int i;
 389
 390         sch->limit = 10*1024;
 391         q->flows_cnt = 1024;
 392         q->quantum = psched_mtu(qdisc_dev(sch));
 393         q->perturbation = net_random();
 394         INIT_LIST_HEAD(&q->new_flows);
 395         INIT_LIST_HEAD(&q->old_flows);
 396         codel_params_init(&q->cparams);
 397         codel_stats_init(&q->cstats);
 398         q->cparams.ecn = true;
 399
 400         if (opt) {
 401                 int err = fq_codel_change(sch, opt);
 402                 if (err)
 403                         return err;
 404         }
 405
 406         if (!q->flows) {
 407                 q->flows = fq_codel_zalloc(q->flows_cnt *
 408                                            sizeof(struct fq_codel_flow));
 409                 if (!q->flows)
 410                         return -ENOMEM;
 411                 q->backlogs = fq_codel_zalloc(q->flows_cnt * sizeof(u32));
 412                 if (!q->backlogs) {
 413                         fq_codel_free(q->flows);
 414                         return -ENOMEM;
 415                 }
 416                 for (i = 0; i < q->flows_cnt; i++) {
 417                         struct fq_codel_flow *flow = q->flows + i;
 418
 419                         INIT_LIST_HEAD(&flow->flowchain);
 420                         codel_vars_init(&flow->cvars);
 421                 }
 422         }
 423         if (sch->limit >= 1)
 424                 sch->flags |= TCQ_F_CAN_BYPASS;
 425         else
 426                 sch->flags &= ~TCQ_F_CAN_BYPASS;
 427         return 0;
 428 }
 429
 430 static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb)
 431 {
 432         struct fq_codel_sched_data *q = qdisc_priv(sch);
 433         struct nlattr *opts;
 434
 435         opts = nla_nest_start(skb, TCA_OPTIONS);
 436         if (opts == NULL)
 437                 goto nla_put_failure;
 438
 439         if (nla_put_u32(skb, TCA_FQ_CODEL_TARGET,
 440                         codel_time_to_us(q->cparams.target)) ||
 441             nla_put_u32(skb, TCA_FQ_CODEL_LIMIT,
 442                         sch->limit) ||
 443             nla_put_u32(skb, TCA_FQ_CODEL_INTERVAL,
 444                         codel_time_to_us(q->cparams.interval)) ||
 445             nla_put_u32(skb, TCA_FQ_CODEL_ECN,
 446                         q->cparams.ecn) ||
 447             nla_put_u32(skb, TCA_FQ_CODEL_QUANTUM,
 448                         q->quantum) ||
 449             nla_put_u32(skb, TCA_FQ_CODEL_FLOWS,
 450                         q->flows_cnt))
 451                 goto nla_put_failure;
 452
 453         nla_nest_end(skb, opts);
 454         return skb->len;
 455
 456 nla_put_failure:
 457         return -1;
 458 }
 459
 460 static int fq_codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
 461 {
 462         struct fq_codel_sched_data *q = qdisc_priv(sch);
 463         struct tc_fq_codel_xstats st = {
 464                 .type                           = TCA_FQ_CODEL_XSTATS_QDISC,
 465         };
 466         struct list_head *pos;
 467
 468         st.qdisc_stats.maxpacket = q->cstats.maxpacket;
 469         st.qdisc_stats.drop_overlimit = q->drop_overlimit;
 470         st.qdisc_stats.ecn_mark = q->cstats.ecn_mark;
 471         st.qdisc_stats.new_flow_count = q->new_flow_count;
 472
 473         list_for_each(pos, &q->new_flows)
 474                 st.qdisc_stats.new_flows_len++;
 475
 476         list_for_each(pos, &q->old_flows)
 477                 st.qdisc_stats.old_flows_len++;
 478
 479         return gnet_stats_copy_app(d, &st, sizeof(st));
 480 }
 481
 482 static struct Qdisc *fq_codel_leaf(struct Qdisc *sch, unsigned long arg)
 483 {
 484         return NULL;
 485 }
 486
 487 static unsigned long fq_codel_get(struct Qdisc *sch, u32 classid)
 488 {
 489         return 0;
 490 }
 491
 492 static unsigned long fq_codel_bind(struct Qdisc *sch, unsigned long parent,
 493                               u32 classid)
 494 {
 495         /* we cannot bypass queue discipline anymore */
 496         sch->flags &= ~TCQ_F_CAN_BYPASS;
 497         return 0;
 498 }
 499
 500 static void fq_codel_put(struct Qdisc *q, unsigned long cl)
 501 {
 502 }
 503
 504 static struct tcf_proto **fq_codel_find_tcf(struct Qdisc *sch, unsigned long cl)
 505 {
 506         struct fq_codel_sched_data *q = qdisc_priv(sch);
 507
 508         if (cl)
 509                 return NULL;
 510         return &q->filter_list;
 511 }
 512
 513 static int fq_codel_dump_class(struct Qdisc *sch, unsigned long cl,
 514                           struct sk_buff *skb, struct tcmsg *tcm)
 515 {
 516         tcm->tcm_handle |= TC_H_MIN(cl);
 517         return 0;
 518 }
 519
 520 static int fq_codel_dump_class_stats(struct Qdisc *sch, unsigned long cl,
 521                                      struct gnet_dump *d)
 522 {
 523         struct fq_codel_sched_data *q = qdisc_priv(sch);
 524         u32 idx = cl - 1;
 525         struct gnet_stats_queue qs = { 0 };
 526         struct tc_fq_codel_xstats xstats;
 527
 528         if (idx < q->flows_cnt) {
 529                 const struct fq_codel_flow *flow = &q->flows[idx];
 530                 const struct sk_buff *skb = flow->head;
 531
 532                 memset(&xstats, 0, sizeof(xstats));
 533                 xstats.type = TCA_FQ_CODEL_XSTATS_CLASS;
 534                 xstats.class_stats.deficit = flow->deficit;
 535                 xstats.class_stats.ldelay =
 536                         codel_time_to_us(flow->cvars.ldelay);
 537                 xstats.class_stats.count = flow->cvars.count;
 538                 xstats.class_stats.lastcount = flow->cvars.lastcount;
 539                 xstats.class_stats.dropping = flow->cvars.dropping;
 540                 if (flow->cvars.dropping) {
 541                         codel_tdiff_t delta = flow->cvars.drop_next -
 542                                               codel_get_time();
 543
 544                         xstats.class_stats.drop_next = (delta >= 0) ?
 545                                 codel_time_to_us(delta) :
 546                                 -codel_time_to_us(-delta);
 547                 }
 548                 while (skb) {
 549                         qs.qlen++;
 550                         skb = skb->next;
 551                 }
 552                 qs.backlog = q->backlogs[idx];
 553                 qs.drops = flow->dropped;
 554         }
 555         if (gnet_stats_copy_queue(d, &qs) < 0)
 556                 return -1;
 557         if (idx < q->flows_cnt)
 558                 return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
 559         return 0;
 560 }
 561
 562 static void fq_codel_walk(struct Qdisc *sch, struct qdisc_walker *arg)
 563 {
 564         struct fq_codel_sched_data *q = qdisc_priv(sch);
 565         unsigned int i;
 566
 567         if (arg->stop)
 568                 return;
 569
 570         for (i = 0; i < q->flows_cnt; i++) {
 571                 if (list_empty(&q->flows[i].flowchain) ||
 572                     arg->count < arg->skip) {
 573                         arg->count++;
 574                         continue;
 575                 }
 576                 if (arg->fn(sch, i + 1, arg) < 0) {
 577                         arg->stop = 1;
 578                         break;
 579                 }
 580                 arg->count++;
 581         }
 582 }
 583
 584 static const struct Qdisc_class_ops fq_codel_class_ops = {
 585         .leaf           =       fq_codel_leaf,
 586         .get            =       fq_codel_get,
 587         .put            =       fq_codel_put,
 588         .tcf_chain      =       fq_codel_find_tcf,
 589         .bind_tcf       =       fq_codel_bind,
 590         .unbind_tcf     =       fq_codel_put,
 591         .dump           =       fq_codel_dump_class,
 592         .dump_stats     =       fq_codel_dump_class_stats,
 593         .walk           =       fq_codel_walk,
 594 };
 595
 596 static struct Qdisc_ops fq_codel_qdisc_ops __read_mostly = {
 597         .cl_ops         =       &fq_codel_class_ops,
 598         .id             =       "fq_codel",
 599         .priv_size      =       sizeof(struct fq_codel_sched_data),
 600         .enqueue        =       fq_codel_enqueue,
 601         .dequeue        =       fq_codel_dequeue,
 602         .peek           =       qdisc_peek_dequeued,
 603         .drop           =       fq_codel_drop,
 604         .init           =       fq_codel_init,
 605         .reset          =       fq_codel_reset,
 606         .destroy        =       fq_codel_destroy,
 607         .change         =       fq_codel_change,
 608         .dump           =       fq_codel_dump,
 609         .dump_stats =   fq_codel_dump_stats,
 610         .owner          =       THIS_MODULE,
 611 };
 612
 613 static int __init fq_codel_module_init(void)
 614 {
 615         return register_qdisc(&fq_codel_qdisc_ops);
 616 }
 617
 618 static void __exit fq_codel_module_exit(void)
 619 {
 620         unregister_qdisc(&fq_codel_qdisc_ops);
 621 }
 622
 623 module_init(fq_codel_module_init)
 624 module_exit(fq_codel_module_exit)
 625 MODULE_AUTHOR("Eric Dumazet");
 626 MODULE_LICENSE("GPL");